Psicose is a C-3 epimer of D-fructose which is 70% as sweet as D-fructose. Unlike D-fructose, psicose is largely unmetabolized in the body, and thus finds application as a sugar ingredient of various functional foods for use in blood sugar control, dental cavity prevention, and hepatic lipogenesis inhibition.
Sugar alcohols, widely used as alternatives to sugar, have the side effect of causing diarrhea upon uptake of a certain amount or more whereas no side effects are known for psicose.
Hence, psicose has attracted intensive interest to the use thereof as a sweetener, but since psicose is rarely found in nature, its effective production is a premise for application to the food industry.
Conventionally, psicose is chemically produced from D-fructose through the catalysis of molybdic acid ions. In the meantime, a biological method using a psicose epimerase from Agrobacterium tumefaciens has recently been known as one of the most efficient approaches. The chemical method suffers from the disadvantage of producing only a very small amount of psicose during molasses treatment or glucose isomerization, the process is expensive, and it generates by-products. Also, the biological method is disadvantageous in that the production is of high cost and is low in yield.
Therefore, there is a need for a method by which psicose can be produced at a temperature and pH condition suited for industrialization, with high yields and no by-product generation.